We propose to use SAXS to measure DNA bending in complexes between DNA and the Switch Activation Protein SAP1 from the yeast S. pombe. Preliminary data taken at the SSRL provides strong evidence for a dimer of SAP1 in solution; dimerization occurs through an unusually long coiled-coil region. The DNA binding region is still unknown as well as the degree of bending of the DNA in solution, upon protein binding. We will use long substrate oligonucleotides to measure the DNA bending and will also calibrate the method using the CAP-DNA complex, whose 3D structure is known from X-ray crystallography.